Surface position detection apparatus, exposure apparatus, and exposure method

ABSTRACT

A surface position detection apparatus capable of highly precisely detecting the surface position of a surface to be detected without substantially being affected by relative positional displacement due to a polarization component occurring in a light flux having passed through a reflective surface. In the apparatus, a projection system has a projection side prism member ( 7 ) having first reflective surfaces ( 7   b,    7   c ), and a light receiving system has a light receiving prism member ( 8 ) having second reflective surfaces ( 8   b,    8   c ) arranged in correspondence with the projection side prism member. The surface position detection apparatus further has a member for compensating relative positional displacement due to a polarization component of a light flux having passed through the first and second reflective surfaces.

This application is a continuation of U.S. Pat. No. 8,149,382, filedJul. 15, 2008, which is the National Stage of International ApplicationNo. PCT/JP2006/312852, filed Jun. 28, 2006, which claims priority toJapanese Patent Application No. 2005-200178, filed Jul. 8, 2005, thedisclosures of which are all incorporated herein by reference in theirentirety.

TECHNICAL FIELD

The present invention relates to a surface position detection apparatus,an exposure apparatus, and an exposure method. More particularly, thepresent invention relates to detection of the surface position of aphotosensitive substrate in a projection exposure apparatus used totransfer a mask pattern onto the photosensitive substrate in alithography process for manufacturing a device such as a semiconductordevice, a liquid crystal display device, an imaging device, and athin-film magnetic head.

BACKGROUND ART

A surface position detection apparatus that detects a surface positionusing diagonal incident light described in Japanese Laid-Open PatentPublication No. 2001-296105 and corresponding U.S. Pat. No. 6,897,462(Patent Document 1) is known in the art as a surface position detectionapparatus optimal for use as a projection exposure apparatus. To improvethe detection accuracy of the surface position of a detected surfacetheoretically, the diagonal incident light type surface positiondetection apparatus is required to increase (toward 90 degrees) theincidence angle of a light beam that enters the detected surface. Toprevent the structure and arrangement of a projection optical system anda condensing optical system. of the surface position detection apparatusfrom being restricted by the detected surface, a prism having a pair ofparallel inner reflection surfaces is arranged in an optical path of theprojection optical system and in an optical path of the condensingoptical system so as to arrange the projection optical system and thecondensing optical system distant from the detected surface (refer toFIG. 7 in Patent Document 1).

-   Patent Document 1: Japanese Laid-Open Patent Publication No    2001-296105

DISCLOSURE OF THE INVENTION Problems that are to be Solved by theInvention

However, in the conventional surface position detection apparatusdescribed in FIG. 7 of Patent Document 1, a light beam reflected totallyby the two parallel inner reflection surfaces of the projection siderhombic prism may cause relative displacement of polarizationcomponents. As a result, a clear pattern image may not be formed on thedetected surface. In the same manner, a light beam reflected totally bythe two parallel inner reflection surfaces of the light receiving siderhombic prism may cause relative displacement of polarizationcomponents. This may result in a secondary image of the pattern becomingfurther bluredly.

In an exposure apparatus, when such a conventional surface positiondetection apparatus is used to detect the surface position of a wafer(photosensitive substrate) of which surface is coated with a resist, thereflectivity of light with a specific polarization component is known tochange in accordance with the thickness of the resist layer. Due to therelative displacement of polarization components in the light beampassing through the inner reflection surfaces of rhombic prisms andreflectivity changes caused by the thickness of the resist layer of thephotosensitive substrate, detection errors of the surface position ofthe detected surface are apt to occur in the conventional surfaceposition detection apparatus.

In view of the above problem, it is an object of the present inventionto provide a surface position detection apparatus that detects thesurface position of a detected surface with high precision without beingvirtually affected by relative displacement of polarization componentsin a light beam passing through a reflection surface. It is also anobject of the present invention to provide an exposure apparatus, anexposure method, and a device manufacturing method that enable a patternsurface of a mask and an exposed surface of a photosensitive substrateto be aligned with a projection optical system with high precision usinga surface position detection apparatus that detects the surface positionof a detected surface with high precision

Solutions for Solving the Problems

To solve the above problem, a first aspect of the present inventionprovides a surface position detection apparatus including a projectionsystem which projects a light beam in a diagonal direction onto adetected surface and a light receiving system which receives a lightbeam reflected by the detected surface. The surface position detectionapparatus detects a surface position of the detected surface based on anoutput of the light receiving system. The projection system includes afirst reflection surface. The light receiving system includes a secondreflection surface. The surface position detection apparatus furtherincludes a displacement offset member which offsets relativedisplacement of polarization components in a light beam passing throughthe first reflection. surface of the projection system and the secondreflection surface of the light receiving system.

A second aspect of the present invention provides a surface positiondetection apparatus including a projection system which projects a lightbeam in a diagonal direction onto a detected surface and a lightreceiving system which receives a light beam reflected by the detectedsurface. The surface position detection apparatus detects a surfaceposition of the detected surface based on an output of the lightreceiving system. At least one of the projection system and the lightreceiving system includes a reflection surface. The surface positiondetection apparatus further includes a displacement offset member whichoffsets relative displacement of polarization components in a light beampassing through the reflection surface.

A third aspect of the present invention provides a surface positiondetection apparatus including a projection system which projects a lightbeam in a diagonal direction onto a detected surface and a lightreceiving system which receives a light beam reflected by the detectedsurface. The surface position detection apparatus detects a surfaceposition of the detected surface based on an output of the lightreceiving system. The projection system includes a first reflectionsurface and a projection side depolarizer arranged at a light-emittingside of the first reflection surface. The light receiving systemincludes a second reflection surface arranged in correspondence with thefirst reflection surface and a light receiving side depolarizer arrangedat a light entering side of the second reflection surface.

A fourth aspect of the present invention provides an exposure apparatusfor projecting and exposing a predetermined pattern onto aphotosensitive substrate with a projection optical system. The exposureapparatus includes a surface position detection apparatus according toany one of the first to third aspects for detecting a surface positionof the predetermined pattern surface or an exposed surface of thephotosensitive substrate with respect to the projection optical systemas the surface position of the detected surface. An alignment meansaligns the predetermined pattern surface or the exposed surface of thephotosensitive substrate with the projection optical system based on adetection result of the surface position detection apparatus.

A fifth aspect of the present invention provides an exposure method forprojecting and exposing a predetermined pattern onto a photosensitivesubstrate with a projection optical system. The exposure method includesa detection step of using the surface position detection apparatusaccording to any one of the first to third aspects to detect a surfaceposition of the predetermined pattern surface or an exposed surface thephotosensitive substrate with respect to the projection optical systemas the surface position of the detected surface, and an alignment stepof aligning the predetermined pattern surface or the exposed surface ofthe photosensitive substrate with the projection optical system based ona detection result of the detection step.

A sixth aspect of the present invention provides a device manufacturingmethod including an exposure step of projecting and exposing apredetermined pattern onto a photosensitive substrate with a projectionoptical system, a detection step of using the surface position detectionapparatus according to any one of the first to third aspects to detect asurface position of the predetermined pattern surface or an exposedsurface of the photosensitive substrate with respect to the projectionoptical system as the surface position of the detected surface, analignment step of aligning the predetermined pattern surface or theexposed surface of the photosensitive substrate with the projectionoptical system based on a detection result of the detection step, and adevelopment step of developing the photosensitive substrate that hasundergone the exposure step.

A seventh aspect of the present invention provides a method formanufacturing a surface position detection apparatus including aprojection system, which projects a light beam in a diagonal directiononto a detected surface, and a light receiving system, which. receives alight beam reflected by the detected surface. The surface positiondetection apparatus detects a surface position of the detected surfacebased on an output of the light receiving system. The method includesthe steps of preparing a first reflection surface arranged in theprojection system, preparing a second reflection surface arranged in thelight receiving system, and offsetting relative displacement ofpolarization components in a light beam passing through the firstreflection surface of the projection system and the second reflectionsurface of the light receiving system.

An eighth aspect of the present invention provides an adjustment methodfor a surface position detection apparatus including a projectionsystem, which projects a light beam through a first reflection surfacein a diagonal direction onto a detected surface, and a light receivingsystem, which receives a light beam reflected by the detected surfacethrough a second reflection surface. The surface position detectionapparatus detects a surface position of the detected surface based on anoutput of the light receiving system. The adjustment method includes thesteps of preparing a polarizing member for generating an emission lightbeam having different characteristics in accordance with polarizationcomponents of an incident light beam, and using the polarizing member tooffset relative displacement of polarization components in a light beampassing through the first reflection surface of the projection systemand the second reflection surface of the light receiving system.

Effect of the Invention

A surface position detection apparatus according to a typical aspect ofthe present invention includes an offset element arranged in a pupilspace of a projection system or in a pupil space of a light receivingsystem to change the travel direction of an emission light beam by adifferent angle in accordance with the deflection direction of anincident light beam or an offset element arranged in an object space oran image space of a projection system or in an object space or an imagespace of a light receiving system to shift in parallel the traveldirection of an emission light beam by a different distance from thedeflection direction of an incident light beam as a displacement offsetmember for offsetting relative displacement of polarization componentsin a light beam passing through a reflection surface of at least one ofthe projection system and the light receiving system. The offset elementfunctions to enable the surface position of a detected surface to bedetected with high precision without substantially being affected byrelative displacement of polarization components in a light beam passingthrough the reflection surface or the like.

Further, a surface position detection apparatus according to anotheraspect of the present invention includes a depolarizer for reducingrelative displacement of polarization components in a light beam passingthrough a reflection surface in a projection system and a reflectionsurface in a light receiving system. The depolarizer enables the surfaceposition of a detected surface to be detected with high precisionwithout being substantially affected by relative displacement ofpolarization components of a light beam passing through the reflectionsurface or the like.

Accordingly, when the surface position detection apparatus of thepresent invention is applied to detect the surface position of aphotosensitive substrate with respect to a projection optical system inan exposure apparatus, the surface position detection apparatus detectsthe surface position of the detected surface with high precision withoutbeing substantially affected by relative displacement of polarizationcomponents in a light beam passing through the reflection surface or thelike and enables a pattern surface of a mask to be aligned with anexposed surface of the photosensitive substrate relative to theprojection optical system with high precision. This enables a device tobe manufactured in a satisfactory manner.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram showing the structure of an exposureapparatus including a surface position detection apparatus according toan embodiment of the present invention;

FIG. 2 is a schematic optical path diagram illustrating that aprojection optical system and a condensing optical system shown in FIG.1 are both-side telecentric;

FIG. 3 is a schematic diagram showing the structure between a pair ofpentaprisms in the surface position detection apparatus of the presentembodiment;

FIG. 4 is a perspective diagram showing a detected surface Wa on which aprimary image of a lattice pattern 3 a is formed;

FIG. 5 is a schematic diagram showing the structure of a light receivingslit S having five rectangular open portions Sa1 to Sa5 elongated in theX-direction;

FIG. 6 shows a light receiving surface 14 a of a light receiving unit 14on which five silicon photodiodes PD1 to PD5 are arranged to opticallycorrespond to the open portions Sa1 to Sa5 of the light receiving slitS;

FIG. 7 is a diagram illustrating the structure and operation of adisplacement offset member arranged in the surface position detectionapparatus of the present embodiment;

FIG. 8 is a diagram illustrating the main structure and operation of afirst modification of the present embodiment;

FIG. 9 is a diagram illustrating the main structure and operation of asecond modification of the present embodiment;

FIG. 10 is a diagram illustrating the main structure and operation of athird modification of the present embodiment;

FIG. 11 is a flowchart illustrating the procedures for forming asemiconductor device serving as a microdevice; and

FIG. 12 is a flowchart illustrating the procedures for forming a liquidcrystal display device serving as a microdevice.

DESCRIPTION OF REFERENCE NUMERALS

-   1 light source-   2 condenser lens-   3 deflection prism-   4, 5 projection optical system-   9 pentaprism-   7, 8 rhombic prism-   10, 11 condensing optical system-   12 oscillating mirror-   13 perspective correction prism-   14 a, 14 b relay optical system-   15 light receiving unit-   16 mirror driving unit-   17 position detection unit-   18 correction amount calculation unit-   19 Nomarski prism (first offset element)-   20 beam displacer (second offset element)-   21 wafer holder-   22 holder supporting mechanism-   23 holder driving unit-   31 half-wave plate (phase member)-   32, 33 depolarizer-   IL illumination system-   R reticle-   RH reticle holder-   PL protection optical system-   W wafer

BEST MODE FOR CARRYING OUT THE INVENTION

One embodiment of the present invention will now be described withreference to the accompanying drawings. FIG. 1 is a schematic diagramshowing the structure of an exposure apparatus that includes a surfaceposition detection apparatus according to the embodiment of the presentinvention. FIG. 2 is an optical path diagram showing that a projectionoptical system and a condensing optical system in FIG. 1 are both-sidetelecentric. FIG. 3 is a schematic diagram showing the structure betweena pair of pentaprisms in the surface position detection apparatusaccording to the embodiment of the present embodiment.

To make the drawings clear, FIGS. 1 and 2 do not show the structurebetween the pentaprisms 6 and 9. in FIG. 1, a the Z-axis is set to beparallel to an optical axis AX of a projection optical system PL, aY-axis is set to be parallel to the plane of FIG. 1 within a planeorthogonal to the optical axis AX, and an X-axis is set to be orthogonalto the plane of FIG. 1. In the present embodiment, the surface positiondetection apparatus of the present invention is used to detect thesurface position of a photosensitive substrate in a projection exposureapparatus.

The shown exposure apparatus includes an illumination system. IL forilluminating a reticle R used as a mask, on which a predeterminedpattern is formed, with illumination light (exposure light) emitted froman exposure light source (not shown). A reticle holder RH supports thereticle R on a reticle stage (not shown) in a manner that the reticle Ris parallel to the XY plane. The reticle stage is movable in atwo-dimensional manner along a reticle surface (that is, the XY plane)when driven by a drive system (not shown). The coordinates representingthe position of the reticle stage are measured by a reticleinterferometer (not shown) to control the position of the reticle stage.

Light from the pattern. of the reticle R enters the projection opticalsystem PL, which forms a pattern image of the reticle R on a surface(exposed surface) Wa of a wafer W, which is a photosensitive substrate.The wafer W is held on a wafer holder 21, and the wafer holder 21 issupported by a holder supporting mechanism 22. The holder supportingmechanism 22 supports the wafer holder 21 with three support points 22 ato 22 c (only two support points 22 a and 22 h are shown in FIG. 1),which are movable in upward and downward directions (Z-direction).

A holder driving unit 23 controls the upward and downward movement ofthe support points 22 a to 22 c of the holder supporting mechanism 22 tolevel and move the wafer holder 21 in the Z-direction (focusingdirection). This consequently levels and moves the wafer W in theZ-direction. The wafer holder 21 and the holder supporting mechanism 22are further supported on a wafer stage (not shown). The wafer stage ismovable in a two-dimensional manner along a wafer surface (i.e., the XYplane) when driven by a drive mechanism (not shown) and is alsorotatable about the Z-axis. The coordinates representing the position ofthe wafer stage are measured by a wafer interferometer (not shown) tocontrol the position of the wafer stage.

To transfer a circuit pattern formed on the pattern surface of thereticle R onto exposure fields of the exposed surface Wa of the wafer Win a satisfactory manner, each exposure field in the exposed surface Wamust be positioned during exposure within the range of the focal depthof the projection optical system PL that is centered about an imagingplane of the projection optical system PL. To position an exposurefield, the surface positions of points in the present exposure field,that is, surface position along the optical axis AX of the projectionoptical system PL may first be accurately detected. Then, the waferholder 21 may be leveled and moved in the Z-direction to consequentlylevel and move the wafer W in the Z-direction so that the exposedsurface Wa falls within the range of the focal depth of the projectionoptical system PL.

Accordingly, the projection exposure apparatus of the present embodimentincludes a surface position detection apparatus for detecting thesurface position of each point within the present exposure field of theexposed surface Wa. Referring to FIG. 1, the surface position detectionapparatus of the present embodiment includes a light source 1 forsupplying detection light. The surface Wa of the wafer W, which servesas the detected surface, is normally coated with a thin film of resistor the like. To reduce the influence of interference between light andthe thin film, it is preferable that the light source 1 be a white lightsource having a wide wavelength range (e.g., a halogen lamp thatsupplies illumination light having a wavelength range of 600 to 900 nmor a xenon light source that supplies illumination light in a similarband as the halogen lamp). A light emitting diode that supplies light ina wavelength band in which resist has weak photosensitivity may also beused as the light source 1.

A divergent beam from the light source 1 is converted to a generallyparallel beam by a condenser lens 2 and then enters a deflection prism3. The deflection prism 3 deflects the generally parallel light beamfrom the condenser lens 2 in the −Z direction by refracting the lightbeam. A transmissive lattice pattern 3 a is formed at a light-emittingside of the deflection prism 3. The transmissive lattice pattern 3 a isformed by alternately arranging elongate light transmitting portionsextending in the X-direction and elongated light shielding portionsextending in the X-direction at regular intervals. Alternatively, areflective diffraction grating having projections and recesses or areflective lattice pattern formed by alternately forming reflectiveportions and nonreflective portions may be used in lieu of thetransmissive lattice pattern.

Light passing through the transmissive lattice pattern 3 a enters aprojection optical system (4 and 5), which is arranged along an opticalaxis AX1 that is parallel to the optical axis AX of the projectionoptical system. The projection optical system (4 and 5) is formed by aprojection condenser lens 4 and a projection optical lens 5. A lightbeam passing through the projection optical system (4 and 5) enters apentaprism 6. The pentaprism 6 is a pentagonal deflection prism with alongitudinal axis extending in the X-direction. The pentaprism 6 has afirst transmissive surface 6 a for transmitting incident light along theoptical axis AX1 without refracting the incident light. The firsttransmissive surface 6 a is set to be orthogonal to the optical axisAX1.

Light passing through the first transmissive surface 6 a and propagatinginside the pentaprism 6 along the optical axis AX1 is reflected by afirst reflection surface 6 b and then reflected again by a secondreflection. surface 6 c along an optical axis AX2. The light reflectedby the second reflection surface 6 c and propagating inside thepentaprism 6 along the optical axis AX2 passes through a secondtransmissive surface 6 d without being refracted by the secondtransmissive surface 6 d. The second transmissive surface 6 d is set tobe orthogonal to the optical axis AX2. The pentaprism 6 is formed froman optical material having low thermal expansion and low divergentproperties, such as quartz glass. A reflection film made of, forexample, aluminum or silver is formed on the first reflection surface 6b and the second reflection surface 6 c.

Light entering the pentaprism 6 in the −Z direction along the opticalaxis AX1 is significantly deflected by the pentaprism 6 and guided alongthe optical axis AX2 toward the detected surface Wa. The direction ofthe optical axis AX2 is set so that the incidence angle on the detectedsurface Wa is sufficiently large. This consequently sets the deflectionangle at which the light is deflected by the pentaprism 6. Morespecifically, as shown in FIG. 3, a light beam emitted from thepentaprism 6 along the optical axis AX2 enters a projection side rhombicprism 7.

The rhombic prism 7 is a quadratic prism having a rhombic cross-section.The longitudinal axis of the rhombic prism 7 extends in the X-directionin the same manner as the pentaprism 6. In the rhombic prism 7, lightpassing through a first transmissive surface 7 a, which is orthogonal tothe optical axis AX2, is sequentially reflected by two parallelreflection surfaces 7 b and 7 c and then passes through a secondtransmissive surface 7 d, which is parallel to the first transmissivesurface 7 a. The light is then emitted from the rhombic prism 7 along anoptical axis AX21 that is parallel to the optical axis AX2. The lightbeam emitted from the rhombic prism 7 along the optical axis AX21 entersthe detected surface Wa.

In a state in which the detected surface Wa coincides with an imagingplane of the projection optical system PL, the projection optical system(4 and 5) is formed so that the surface on which the lattice pattern 3 ais formed (that is, the light emitting surface of the deflection prism3) and the detected surface Wa are conjugate to each other. Also, thesurface on which the lattice pattern 3 a is formed and the detectedsurface Wa satisfy the Scheimpflug condition with respect to theprojection optical system (4 and 5). As a result, light from the latticepattern 3 a is precisely focused over the entire pattern image formationsurface of the detected surface Wa with the projection optical system (4and 5).

The optical path indicated by a broken line in FIG. 2 shows that theprojection optical system (4 and 5), which is formed by the projectioncondenser lens 4 and the projection objective lens 5, is a both-sidetelecentric optical system. Accordingly, points on the formation surfaceof the lattice pattern 3 a and the detected surface Wa that areconjugate to each other have the same magnification over the entiresurfaces. In this manner, referring to FIG. 4, a primary image of thelattice pattern 3 a is accurately formed over the entire detectedsurface Wa.

Referring again to FIG. 1, a light beam reflected by the detectedsurface Wa along an optical axis AX31, which is symmetric to the opticalaxis AX21 with respect to the optical axis AX of the projection opticalsystem PL, enters a light receiving side rhombic prism 8. The rhombicprism 8 is a quadratic prism having a longitudinal axis extending in theX-direction and having a rhombic cross-section like the rhombic prism 7.In the rhombic prism 8, light passing through a first transmissivesurface 8 a, which is orthogonal to the optical axis AX31, issequentially reflected by two parallel reflection surfaces 8 b and 8 cand then passes through a second transmissive surface 8 d, which isparallel to the first transmissive surface 8 a. The light is emittedfrom the rhombic prism 8 along an optical axis AX3, which is parallel tothe optical axis AX31.

The light emitted from the rhombic prism 8 along the optical axis AX3enters a condensing optical system (10 and 11) after passing through apentaprism 9, which has the same structure as the pentaprism 6 describedabove. More specifically, light reflected by the detected surface Waenters the pentaprism 9 along the optical axis AX3, which is symmetricto the optical axis AX2 with respect to the optical axis AX of theprojection optical system PL. In the pentaprism 9, light passing througha first transmissive surface 9 a, which is orthogonal to the opticalaxis AX3, is sequentially reflected by a first reflection surface 9 band a second reflection surface 9 c and then reaches a secondtransmissive surface 9 d along an optical axis AX4 extending in theZ-direction. Light passing through the second transmissive surface 9 d,which is orthogonal to the optical axis AX4, enters the condensingoptical system (10 and 11) in the +Z direction along the optical axisAX4.

The condensing optical system (10 and 11) is formed by a light receivingobjective lens 10 and a light receiving condenser lens 11. Anoscillating mirror 12, which serves as a scanning means, is arranged inan optical path formed between the light receiving objective lens 10 andthe light receiving condenser lens 11. Thus, light entering the lightreceiving objective lens 10 along the optical axis AX4 is deflected bythe oscillating mirror 12 and reaches the light receiving condenser lens11 along an optical axis AX5. In the present embodiment, the oscillatingmirror 12 is generally arranged at a pupil plane of the condensingoptical system (10 and 11). However, the present invention is notlimited in such a manner and the oscillating mirror 12 may be arrangedat any position in the optical path formed between the detected surfaceWa and a perspective correction prism 13, which will be described later,or at an optical path formed between the detected surface Wa and thedeflection prism 3.

Light passing through the condensing optical system (10 and 11) entersthe perspective correction prism 13, which has the same structure as thedeflection prism 3. In a state in which the detected surface Wacoincides with the imaging plane of the projection optical system PL,the condensing optical system (10 and 11) is formed so that the detectedsurface Wa and a light entering surface 13 a of the perspectivecorrection prism 13 are conjugate to each other. With this structure, asecondary image of the lattice pattern 3 a is formed on the lightentering surface 13 a of the perspective correction prism 13.

The light entering surface 13 a of the perspective correction prism 13includes a light receiving slit 5, which serves as a light shieldingmeans. As shown in FIG. 5, the light receiving slit S may include, forexample, five open portions Sa1 to Sa5, each of which has an elongatedrectangular shape extending in the X-direction. Light reflected from thedetected surface Wa and passing through the condensing optical system(10 and 11) enters the perspective correction prism 13 through the openportions Sa1 to Sa5 of the light receiving slit S.

The number of the open portions Sa of the light receiving slit Scorresponds to the number of detection points on the detected surfaceWa. FIG. 4 shows the detected surface Wa on which a primary image of thelattice pattern 3 a is formed. In this state, detection points(detection regions) Da1 to Da5 on the detected surface Wa opticallycorrespond to the five open portions Sa1 to Sa5 of the light receivingslit S shown in FIG. 5. The number of detection points on the detectedsurface Wa may be increased by just increasing the number of openportions Sa. An increase in the number of detection points does not makethe structure complicated.

The imaging plane of the projection optical system PL and the lightentering surface 13 a of the perspective correction prism 13 satisfy theScheimpflug condition with respect to the condensing optical system (10and 11). Accordingly, in a state in which the detected surface We andthe imaging plane coincide with each other, light from the latticepattern 3 a is accurately focused again over the entire pattern imageformation surface on the prism light entering surface 13 a by thecondensing optical system (10 and 11).

As shown by the optical path indicated by a broken line in FIG. 2, thecondensing optical system (10 and 11) is a two-side telecentric opticalsystem. Accordingly, points on the detected surface Wa and conjugatepoints on the prism light entering surface 13 a have the samemagnification over the entire surface. Thus, a secondary image of thelattice pattern 3 a is accurately formed over the entire light enteringsurface 13 a of the perspective correction prism 13.

When a light receiving surface is located at the light entering surface13 a of the perspective correction prism 13, an incidence angle θ of alight beam on the detected surface Wa is large. Thus, the incidenceangle of the light beam on the light receiving surface increasesaccordingly. In this case, if, for example, a silicon photodiode isarranged on the light receiving surface, a light beam enters the siliconphotodiode at a large incidence angle. This increases the surfacereflection of the silicon photodiode and causes vignetting. This mayresult in a significant decrease of the light receiving amount.

To prevent the light receiving amount from decreasing due to theincidence angle of a light beam on the light receiving surface, in thepresent embodiment, the light entering surface 13 a of the perspectivecorrection prism 13, which serves as a deflection optical system, isarranged on a surface conjugate to the detected surface Wa with respectto the condensing optical system (10 and 11). As a result, a light beamincident on the light entering surface 13 a of the perspectivecorrection prism 13 along the optical axis AX5 with the condensingoptical system (10 and 11) is deflected at a refraction angle that isthe same as the vertex angle of the perspective correction prism 13(angle formed by the light receiving surface and the light emittingsurface) and then emitted from the light emitting surface 13 b alongoptical axis AX6. The light emitting surface 13 b is set to beorthogonal to the optical axis AX6.

The light beam emitted from the light emitting surface 13 b of theperspective correction prism 13 along the optical axis AX6 enters arelay optical system (14 a and 14 b), which is formed by two lenses 14 aand 14 b. Light passing through the relay optical system (14 a and 14 b)forms an image conjugate to the secondary image of the lattice pattern 3a formed on the light entering surface 13 a of the perspectivecorrection prism 13 and the open portions Sa1 to Sa5 of the lightreceiving slit S on the light receiving surface 15 a of the lightreceiving unit 15. As shown in FIG. 6, five silicon photodiodes PD1 toPD5 formed on the light receiving surface 15 a optically correspond tothe open portions Sa1 to Sa5 of the light receiving slit S.Two-dimensional CCDs (charge-coupled device) or photomultipliers may beused in lieu of the silicon photodiodes.

As described above, in the present embodiment, the perspectivecorrection prism 13 serving as a deflection optical system is used. Thissufficiently decreases the incidence angle of the light beam enteringthe light receiving surface 15 a and prevents the light receiving amountfrom being decreased by the incidence angle of the light beam on thelight receiving surface 15 a. It is preferable that the relay opticalsystem (14 a and 14 b) be a both-side telecentric optical system asshown in FIG. 2. It is further preferable that the light enteringsurface 13 a and the light receiving surface 15 a of the perspectivecorrection prism 13 satisfy the Scheimpflug condition with respect tothe relay optical system (14 a and 14 b).

As described above, the light entering surface 13 a of the perspectivecorrection prism 13 includes the light receiving slit S, which has thefive open portions Sa1 to Sa5. Thus, the light receiving slit Spartially shields light from the secondary image of the lattice pattern3 a formed on the light entering surface 13 a. In other words, only thelight beam from the secondary image of the lattice pattern 3 a that isformed in the regions of the open portions Sa1 to Sa5 of the lightreceiving slit S pass through the perspective correction prism 13 andthe relay optical system (14 a and 14 b) and reach the light receivingsurface 15 a.

In this manner, referring to FIG. 6, images of the open portions Sa1 toSa5 of the light receiving slit S, that is, slit images SL1 to SL5, areformed on the silicon photodiodes PD1 to PD5, which are arranged on thelight receiving surface 15 a of the light receiving unit 15. The slitimages SL1 to SL5 are formed inside the rectangular light receivingregions of the silicon photodiodes PD1 to PD5.

When the detected surface Wa is moved upward and downward in theZ-direction along the optical axis AX of the projection optical systemPL, the secondary image of the lattice pattern 3 a formed on the lightentering surface 13 a of the perspective correction prism 13 isdisplaced laterally in the pitch direction of the pattern in accordancewith the upward and downward movement of the detected surface Wa. In thepresent embodiment, for example, the amount of lateral displacement ofthe secondary image of the lattice pattern 3 a may be detected based onthe principle of a photoelectric microscope disclosed in JapaneseLaid-Open Patent Publication No 6-97045 by the same applicant as thepresent application. The surface position of the detected surface Waalong the optical axis AX of the projection optical system FL may bedetected based on the detected lateral displacement amount.

A mirror driving unit 16 drives the oscillating mirror 12. A positiondetection unit 17 synchronously detects the waveform of detectionsignals from the silicon photodiodes PD1 to PD5 based on an alternatingcurrent signal from the mirror driving unit 16. A correction amountcalculation unit 18 calculates the amount of inclination correction andthe amount of correction in the Z-direction required to position thedetected surface Wa within the range of the focal depth of theprojection optical system PL. The holder driving unit 23 drives theholder supporting mechanism 22 based on the inclination correctionamount and the Z-direction correction amount, levels the wafer holder21, and moves the wafer holder 21 in the Z-direction. Such operations ofthe mirror driving unit 16, the position detection unit 17, thecorrection amount calculation unit 18, and the holder driving unit 23are identical to the operations performed by the apparatuses disclosedin Japanese Laid-Open Patent Publication No. 2001-296105 and itscorresponding U.S. Pat. No. 6,897,462 by the same applicant as thepresent application and will not be described in the present embodiment.

The Scheimpflug condition, the structure and operation of the deflectionprism 3 and the perspective correction prism 13, specific applicationsof the principle of the photoelectric microscope and the like aredescribed in detail in U.S. Pat. No. 5,633,721. The structure andoperation of the pentaprisms 6 and 9 are described in detail in JapaneseLaid-Open Patent Publication No. 2001-296105 and its corresponding U.S.Pat. No. 6,897,462. Either one or both of the pentaprisms 6 and 9 may beeliminated. U.S. Pat. No. 5,633,721 and U.S. Pat. No. 6,897,462 areincorporated herein by reference.

In the present embodiment, the pentaprism 6 is arranged in the opticalpath formed between the projection optical system (4 and 5) and thedetected surface Wa, and the pentaprism 9 is arranged in the opticalpath formed between the condensing optical system (10 and 11) and thedetected surface Wa. The optical path of a light beam incident on thedetected surface Wa and the optical path of a light beam reflected bythe detected surface Wa are deflected by a significant amount by thepentaprisms 6 and 9 so as to arrange the projection optical system (4and 5) and the condensing optical system (10 and 11) at positionssufficiently distant from the detected surface Wa. As a result, thestructure and arrangement of the projection optical system (4 and 5) andthe condensing optical system (10 and 11) are substantially notrestricted by the detected surface Wa.

In the present embodiment, the rhombic prism 7 is arranged in theoptical path formed between the pentaprism 6 and the detected surfaceWa, and the rhombic prism 8 is arranged in the optical path formedbetween the pentaprism 9 and the detected surface Wa. Thus, the opticalpath of a light beam incident on the detected surface Wa and the opticalpath of a light beam reflected from the detected surface W are eachshifted in parallel by the rhombic prisms 7 and 8. As a result, thepentaprisms 6 and 9 are arranged at positions distant from the detectedsurface Wa. The structure and arrangement of the pentaprisms 6 and 9 andtheir supporting members are substantially not restricted by thedetected surface Wa.

The surface position detection apparatus of the present embodimentincludes the projection side prism member, or the rhombic prism 7, andthe light receiving side prism member, or the rhombic prism 8. Therhombic prism 7 includes the two inner reflection surfaces (7 b and 7 c)arranged in the optical path of the projection system to shift inparallel the optical path of an incident light beam. The rhombic prism 8includes the two inner reflection surfaces (8 b and 8 c) arranged incorrespondence with the projection side prism member 7 in the opticalpath of the light receiving system to shift in parallel the optical pathof an incident light beam from the detected surface Wa. In this case,relative displacement of polarization components occurs in a light beamtotally reflected by the two parallel inner reflection surfaces (7 b and7 c) of the projection side rhombic prism 7. As a result, a clearpattern image is not formed on the detected surface Wa.

More specifically, in a light beam reaching the detected surface Wa,relative displacement occurs between p-polarized light and s-polarizedlight with respect to the detected surface Wa. Consequently, a patternimage formed on the detected surface Wa by the p-polarized light and apattern image formed on the detected surface Wa by the s-polarized lightare displaced relative to each other. In the same manner, relativedisplacement of polarization components occurs in a light beam reflectedby the detected surface Wa and totally reflected by the two parallelinner reflection surfaces (8 b and 8 c) of the light receiving siderhombic prism 8. As a result, a secondary image of a pattern formed onthe light entering surface 13 a of the perspective correction prism 13will becomes further unclear.

In other words, the total reflection on the inner reflection surfaces (8b and 8 c) of the light receiving side rhombic prism 8 accentuatesrelative displacement that occurs between a secondary image of a patternformed on the light entering surface 13 a by the p-polarized light and asecondary image of the pattern formed on the light entering surface 13 aby the s-polarized light.

The surface position detection apparatus of the present embodiment isused to detect the surface position of a wafer W that has variousdifferent surface states during a semiconductor exposure process (e.g.,structures on the wafer W being formed from various materials or thewafer W having various structures (multi-layer structure)). The wafersurface is normally coated with a resist. When the surface state of sucha wafer W has variations (e.g., when the thicknesses of a layer formingthe wafer surface has variations or properties such as the purity of amaterial forming the wafer surface layer has variations) or the resistthickness has variations, the reflectivity of the wafer surface to lighthaving specific polarization components (e.g., p-polarised light ors-polarized light) changes in accordance with such variations.

If no countermeasures are taken against such a problem, the surfaceposition detection apparatus of the present embodiment would have atendency of producing detection errors of the surface position of thedetected surface Wa due to the relative displacement of polarizationcomponents in a light beam passing through the inner reflection surfaces(7 b and 7 c or 8 b and 8 c) of the rhombic prisms (7 and 8) and thereflectivity changes of specific polarization components caused by thesurface state variations of the wafer W or the resist thicknessvariations of the wafer W.

In recent years, miniaturization of projection exposure patterns hasresults in a demand for a wafer surface having higher flatness andhigher precision for surface position detection. Further, an exposureapparatus using an ArF excimer laser light source tends to have athinner resist coating on the wafer surface. For such an exposureapparatus, surface position detection errors caused by surface statevariations or resist thickness variations described above cannot beignored.

To cope with this problem, the surface position detection apparatus ofthe present embodiment includes a displacement offset member foroffsetting relative displacement of polarization components in a lightbeam passing through the inner reflection surfaces (7 b and 7 c) of theprojection side prism member (rhombic prism) 7 and the inner reflectionsurfaces (8 b and 8 c) of the light receiving side prism member (rhombicprism) 8.

FIG. 7 is a diagram describing the structure and effects of thedisplacement offset member included in the surface position detectionapparatus of the present embodiment. For the sake of brevity, FIG. 7shows an optical path extending from the detected surface Wa to thelight entering surface 13 a of the perspective correction prism 13 alongthe linear optical axis AX. The oscillating mirror 12 is not shown. Thesame applies to FIG. 8, which is related to FIG. 7. Referring to FIG. 7,the surface position detection apparatus of the present embodimentincludes a Nomarski prism 19, which serves as the displacement offsetmember, at a pupil position of the condensing optical system (10 and 11)in the optical path between the light receiving objective lens 10 andthe light receiving condenser lens 11 or near the pupil position.

The Nomarski prism 19 is an optical element (first offset element)functioning to change the travel direction of an emission light beam bya different angle depending on the polarization direction of an incidentlight beam. More specifically, as shown in FIG. 7, the total reflectionon the inner reflection surfaces (7 b and 7 c or 8 b and 8 c) of therhombic prisms (7 and 8) causes relative displacement between thep-polarized light and the s-polarized light, and representativep-polarized light 71 a and representative s-polarized light 72 a, whichare inclined at different angles with respect to the optical axis AX,enter the Nomarski prism 19 at substantially a single point on theoptical axis AX. Based on its function for changing the travel directionof an emission light beam by the different angle from the polarizationdirection of an incident light beam, the Nomarski prism 19 converts theincident p-polarized light 71 a, which is inclined to the optical axisAX, into p-polarized emission light 71 b that substantially travelsalong the optical axis AX and also converts the incident s-polarizedlight 72 a, which is inclined with respect to the optical axis AX, intos-polarized emission light 72 b that travels substantially along theoptical axis AX.

In this manner, the relative displacement of the p-polarized light andthe s-polarized light caused by the total reflection on the innerreflection surfaces (7 b and 7 c or 8 b and 8 c) of the rhombic prisms(7 and 8) is offset by the Nomarski prism 19. As a result, thep-polarized emission light 71 b and the s-polarized emission light 72 bfrom the Nomarski prism 19 travel along substantially the same path andreach substantially a single point on the light entering surface 13 a ofthe perspective correction prism 13. As a result, the surface positiondetection apparatus of the present embodiment forms a clear secondaryimage of the pattern on the light entering surface 13 a of theperspective correction. prism 13 with the Nomarski prism 19, whichserves as the displacement offset member, and consequently detects thesurface position of the detected surface Wa with high precision withoutbeing virtually affected by relative displacement of polarizationcomponents in a light beam passing through the inner reflection surfaces(7 b and 7 c or 8 b and 8 c) of the prism members (rhombic prisms) 7 and8. Without the Nomarski prism 19, the p-polarized emission light(indicated by a broken line in the drawing) 71 c and the s-polarizedemission light (indicated by a broken line in the drawing) 72 c from theNomarski prism 19 would travel along different paths and reach differentpositions on the light entering surface 13 a of the perspectivecorrection prism 13. In such a case, a sharp secondary image of thepattern would not be formed on the light entering surface 13 a of theperspective correction prism 13.

In the above description, the Nomarski prism is used as the displacementoffset member that functions to change the travel direction of anemission light beam by the different angle from the polarizationdirection of an incident light beam. However, the present invention isnot limited to such a structure. For example, a Wollaston prism may beused in lieu of a Nomarski prism. Further, when a Nomarski prism or aWollaston prism is used as the displacement correction member, adirect-vision prism may be arranged near the Nomarski prism or theWollaston Prism to correct color shifting.

For the sake of simplicity, a wedge prism plate formed from abirefringent crystal material, such as calcite, quartz, yttriumorthovanadate crystal, or rutile crystal, may be used in lieu of theprism to cause an incident ordinary light beam and an incidentextraordinary light beam to travel at different angles. In this case,for example, the crystal optical axis and the wedge are oriented tocause the incident ordinary light beam and the incident extraordinarylight beam to travel at different angles. Alternatively, a structure inwhich such a wedge prism plate and a wedge prism plate made of normaloptical glass are bonded together may be used. In such a case, the sameadvantages are produced as when the above Nomarski prism is used.

In the above description, the Nomarski prism 19 is arranged at or nearthe pupil position of the condensing optical system (10 and 11) in theoptical path formed between the light receiving objective lens 10 andthe condensing objective lens 11. However, the present invention is notlimited to such a structure and the Nomarski prism may be arrangednormally in a pupil space of the projection system or a pupil space ofthe light receiving system. When arranged in the pupil space of aprojection system, the Nomarski prism may be located at or near thepupil position of the projection optical system (4 and 5) in the opticalpath formed between the projection condenser lens 4 and the projectionobjective lens 5. Further, when the Wollaston prism us used as thedisplacement offset member, the Wollaston prism may be arranged in thepupil space of the projection system or the pupil space of the lightreceiving system. However, when the displacement offset member, such asthe Nomarski prism or the Wollaston prism, is added to an existingapparatus to improve performance, it would be easier to arrange thedisplacement offset member in the pupil space of the light receivingsystem than in the pupil space of the projection system.

In the above description, an optical element such as the Nomarski prismand the Wollaston prism) that functions to change the travel directionof an emission light beam by a different angle from the polarizationdirection of an incident light beam is used as the displacement offsetmember. However, the present invention is not limited to such astructure. As shown in FIG. 8, a modification may be made so that anoptical element shifts in parallel the travel direction of an emissionlight beam by a different distance from the polarization direction of anincident light beam (second offset element). Alternatively, as shown inFIG. 9, a modification may be made so that a phase member used as thedisplacement offset member is arranged in an optical path formed betweenthe projection prism member (rhombic prism) 7 and the light receivingside prism member (rhombic prism 8) to change the polarization directionof an incident light beam.

Referring to FIG. 8, a beam displacer 20, which functions as thedisplacement offset member of the first modification, is arranged in anoptical path between the light receiving condenser lens 11 and theperspective correction prism 13. The beam displacer 20 may be formed of,for example, a birefringent crystal material, such as calcite, quartz,yttrium orthovanadate (YVO₄) crystal, or rutile (TiO₂) crystal, andfunctions to emit an incident ordinary light beam and an incidentextraordinary light beam in a manner parallel to each other. In otherwords, the beam displacer 20 functions to shift in parallel the traveldirection of an emission light beam by a different distance from anincident light beam.

More specifically, referring to FIG. 8, relative displacement occursbetween the p-polarized light and s-polarized light due to the influenceof the total reflection on the inner reflection surfaces (7 b and 7 c or8 b and 8 c) of the rhombic prisms (7 and 8). The representativep-polarized light 73 a and s-polarized light 74 a travel along differentpaths that are substantially parallel to the optical axis AX and enterthe beam displacer 20. Based on the function for shifting in parallelthe travel direction of an emission light beam by a different distancefrom the incident light beam, the beam displacer 20 transmits theincident p-polarized light 73 a and converts the p-polarized light 73 ato p-polarized emission light 73 b, which travels along a path thatextends substantially parallel to the optical axis AX, and also shiftsin parallel the incident s-polarized light 74 a to convert thes-polarized light 74 a to s-polarized emission light 74 b that travelssubstantially along the same path as the p-polarized emission light 73b.

In this manner, the beam displacer 20 functions to offset the relativedisplacement of the p-polarized light and the s-polarized light caused.by the total reflection at the inner reflection surfaces (7 b and 7 c or8 b and 8 c) of the rhombic prisms (7 and 8). As a result, thep-polarized light 73 b and the s-polarized, light 74 b emitted from thebeam displacer 20 travel substantially along the same path and reachsubstantially a single point on the light entering surface 13 a of theperspective correction prism 13. As a result, in the first modificationexample shown in FIG. 8, the beam displacer 20, which functions as thedisplacement offset member, also enables a sharp secondary image of apattern to be formed on the light entering surface 13 a of theperspective correction prism 13 and consequently enables the surfaceposition of the detected surface Wa to be detected with high precision.Without the beam displacer 20, the p-polarized light 73 c and thes-polarized light 74 c (indicated by a broken line in the drawing)emitted from the beam displacer 20 would travel along different pathsand reach different positions on the light entering surface 13 a of theperspective correction prism 13. In such a case, a sharp secondary imageof the pattern is not formed on the light entering surface 13 a of theperspective correction prism 13.

In the first modification, the beam displacer 20 is arranged in theoptical path formed between the light receiving condenser lens 11 andthe perspective correction prism 13. In other words, the beam displacer20 is arranged in an image space of the light receiving system. However,the present invention is not limited to such a structure, and the beamdisplacer may generally be arranged in the optical path between thedeflection prism 3 and the perspective correction prism 13, that is, inan object space or an image space of the projection system or an objectspace or an image space of the light receiving system. However, when thedisplacement offset member, such as the beam displacer, is added to anexisting apparatus to improve performance, it is preferable that thedisplacement offset member be arranged in the image space of the lightreceiving system in order to facilitate optical adjustment.

Referring to FIG. 9, a half-wave plate 31, which functions as adisplacement offset member in a second modification, is arranged nearthe light receiving rhombic prism 8 in an optical path formed betweenthe two prism members (rhombic prisms) 7 and 8. The half-wave plate 31,which is a phase member for changing the polarization direction of anincident light beam, functions to convert incident p-polarized light tos-polarized light and emit the s-polarized light and convert incidents-polarized light to p-polarized light and emit the p-polarized light.

In this case, p-polarized light passing through the inner reflectionsurfaces (7 b and 7 c) of the projection side rhombic prism 7 isconverted to s-polarized light by the half-wave plate 31 and passesthrough the inner reflection surfaces (8 b and 8 c) of the lightreceiving side rhombic prism 8. In the same manner, s-polarized lightpassing through the inner reflection surfaces (7 b and 7 c) of theprojection side rhombic prism 7 is converted to p-polarized light by thehalf-wave plate 31 and passes through the inner reflection surfaces (8 band 8 c) of the light receiving side rhombic prism 8. In the secondmodification, displacement of the p-polarized light caused by the totalreflection on the inner reflection surfaces (7 b and 7 c) of theprojection side rhombic prism 7 is offset by displacement of thes-polarized light caused by the total reflection on the inner reflectionsurfaces (8 b and 8 c) of the light receiving side rhombic prism 8.Displacement of the s-polarized light caused by the total reflection onthe inner reflection surfaces (7 b and 7 c) of the projection siderhombic prism 7 is offset by displacement of the p-polarized lightcaused by the total reflection on the inner reflection surfaces (8 b and8 c) of the light receiving side rhombic prism 8. As a result, in thesecond modification shown in FIG. 9, the half-wave plate 31, whichfunctions as the displacement offset member, enables a clear secondaryimage of the pattern to be formed on the light entering surface 13 a ofthe perspective correction prism 13 and consequently enables the surfaceposition of the detected surface Wa to be detected with high precision.

In the second modification described above, the half-wave plate 31 isused as the phase member arranged in the optical path between theprojection side prism member 7 and the light receiving side prism member8 to change the polarization direction of an incident light beam.However, the present invention is not limited to such a structure and aFaraday rotator (Faraday optical rotator) may be used as the phasemember in lieu of the half-wave plate 31.

Further, in the second modification described above, the half-wave plate31, which functions as the phase member, is arranged near the lightreceiving side rhombic prism 8 in the optical path between the pair ofprism members (rhombic prisms) 7 and 8. However, the present inventionis not limited to such a structure, and a phase member, such as ahalf-wave plate, may be arranged at an appropriate position at theprojection side or the light receiving side in the optical path betweenthe pair of prism members (rhombic prisms) 7 and 8.

Also, in the above embodiment and modifications, displacement offsetmembers (19, 20, and 31), which offset the relative displacement ofpolarization components in a light beam passing through the innerreflection surfaces of the projection side prism member 7 and the innerreflection surfaces of the light receiving side prism member 8, areused. However, the present invention is not limited to such a structure.As shown in FIG. 10, a depolarizer for randomly changing thepolarization direction of an incident light beam may be used as a thirdmodification.

In the third modification shown in FIG. 10, a projection sidedepolarizer 32 is arranged near a light-emitting side of a projectionside prism member (rhombic prism) 7 and a light receiving sidedepolarizer 33 is arranged near a light entering side of a lightreceiving side prism member (rhombic prism) 8. The depolarizers 32 and33 may be, for example, deflection prisms (wedge-shaped prisms) formedfrom a birefringent crystal material, such as quartz crystal ormagnesium fluoride, and function to substantially depolarize incidentp-polarized light and incident s-polarized light.

In this case, the polarization direction of light before entering thewafer W and after exiting the wafer W is randomized by the twodepolarizers 32 and 33. This reduces the influence of changes in thereflectivity of the p-polarized light and s-polarized light caused bythe resist layer formed on the wafer W, As a result, in the thirdmodification, the surface position of the detected surface Wa isdetected with high precision without being substantially affected byrelative displacement of polarization components in a light beam passingthrough the inner reflection surfaces (7 b and 7 c or 8 b and 8 c) ofthe prism members (rhombic prisms) 7 and 8,

In the present embodiment, a reflection film, such as a metal film madeof aluminum, may be formed on an outer surface of each of the innerreflection surfaces (7 b and 7 c or 8 b and 8 c) of the projection siderhombic prism 7 and the light receiving side rhombic prism 8. Thisstructure prevents the total reflection phenomenon of the rhombic prisms7 and 8 and substantially prevents relative displacement of polarizationcomponents in a light beam passing through the rhombic prisms 7 and 8.

In the present embodiment, a projection side second rhombic prism may bearranged adjacent to the projection side rhombic prism 7, and a lightreceiving side second rhombic prism may be arranged adjacent to thelight receiving side rhombic prism 8, With this structure, the influenceof the total reflection of the inner reflection surfaces (7 b and 7 c)in the projection side rhombic prism 7 is offset by the influence of thetotal reflection of the inner reflection surfaces in the projection sidesecond rhombic prism. Further, the influence of the total reflection ofthe inner reflection surfaces (8 b and 8 c) in the light receiving siderhombic prism 8 is offset by the influence of the total reflection ofthe inner reflection surfaces in the light receiving side second rhombicprism. This substantially prevents relative displacement caused bypolarization components of a light beam passing through the rhombicprisms 7 and 8.

Further, in the present embodiment, a polarizer for selectivelytransmitting specific polarization components of an incident light beammay be arranged in an optical path of the projection system or anoptical path of the light receiving system. In such a case, the resistlayer formed on the wafer W has a higher reflectivity with respect tos-polarized light than p-polarized light. Thus, it is preferable that apolarizing member be used to selectively transmit only s-polarized lightwith respect to the detected surface Wa. In this structure, only lightwith a specific polarization component is received. This enables thesurface position of the detected surface to be detected with highprecision without being affected by relative displacement ofpolarization components in a light beam passing through the innerreflection surfaces of the prism member or the like. However, the use ofsuch a polarizer is not practical from the viewpoint of light loss.

In the above embodiment, relative displacement between p-polarized lightand s-polarized light is caused by the total reflection in the rhombicprisms (7 and 8), which has inner reflection surfaces. However, relativedisplacement between p-polarized light and s-polarized light may also becaused by reflection on outer reflection surfaces. In the aboveembodiment, a modification may be made so that relative displacementbetween p-polarized light and s-polarized light caused by reflection onsuch outer reflection surfaces is offset.

In the above embodiment, the exposure apparatus includes a singlesurface position detection apparatus. However, the present invention isnot limited to such a structure and a plurality of surface positiondetection apparatuses may be used when necessary to divide a detectionview field. In this case, the apparatuses may be calibrated based on adetection result obtained in a common view field of the detection fieldof a first surface position detection apparatus and the detection fieldof a second surface position detection apparatus.

In the above embodiment, the present invention is applied to thedetection of a surface position of a photosensitive substrate in aprojection exposure apparatus. However, the present invention may beapplied to the detection of a surface position of a mask in a projectionexposure apparatus. Further, in the above embodiment, the presentinvention is applied to the detection of a surface position of aphotosensitive substrate in a projection exposure apparatus. However,the present invention may also be applied to the detection of thesurface position of any normal detected surface.

The surface position detection apparatus and the exposure apparatusaccording to the above embodiment are manufactured by assembling varioussubsystems including elements described in the claims of the presentapplication so as to maintain predetermined mechanical precision,electric precision, and optical precision. To maintain this precision,the optical systems are adjusted to obtain the optical precision, themechanical systems are adjusted to obtain the mechanical precision, andthe electric systems are adjusted to obtain the electric precisionbefore and after the assembling process. The processes for assemblingthe exposure apparatus from the subsystems include mechanicallyconnecting the subsystems to one another, wiring the electric circuits,and piping the pressure circuits. Processes for assembling eachsubsystem are performed before the process for assembling the subsystemsto the exposure apparatus. After the process of assembling the exposureapparatus from the subsystems is completed, the apparatus is subjectedto overall adjustment to obtain the required precision. It is preferablethat the exposure apparatus be manufactured in a clean room underconditions, such as temperature and cleanness, which are controlled.

For example, a method for manufacturing the surface position detectionapparatus of the above embodiment includes a process for preparing afirst reflection surface (7 b and 7 c) arranged in a projection system,a process for preparing a. second reflection surface (8 b and 8 c)arranged in a light receiving system, and a process for offsettingrelative displacement of polarization components in a light beam passingthrough the first reflection surface of the projection system and thesecond reflection surface of the light receiving system.

A method for adjusting the surface position detection apparatus of theabove embodiment includes a process for preparing a polarizing member(19, 20, 31, and 33) for generating an emission light beam having acharacteristic that differs in accordance with a polarization componentof an incident light beam, a process for offsetting relativedisplacement of polarization components in a light beam passing throughthe first reflection surface of the projection system and the secondreflection surface of the light receiving system.

The exposure apparatus of the above embodiment may he used to fabricatemicrodevices (including semiconductor devices, imaging devices, liquidcrystal display devices, and thin-film magnetic heads) by illuminating areticle (mask) with an illumination system (illumination process) andexposing a transfer pattern formed on a mask onto a photosensitivesubstrate with a projection optical system (exposure process). Oneexample of the procedures for fabricating a semiconductor device servingas a microdevice through formation of a predetermined circuit pattern ona photosensitive substrate, such as a wafer, using the exposureapparatus of the present embodiment will now be described with referenceto a flowchart shown in FIG. 11.

In step S301 shown in FIG. 11, a metal film is first vapor-deposited onwafers of a first lot. In step S302, photoresist is applied to the metalfilm formed on each wafer of the first lot. In step S303, an image of apattern formed on a mask is exposed and transferred sequentially ontoshot-regions of each wafer of the first lot through a projection opticalsystem with the use of the exposure apparatus of the present embodiment.In step S304, the photoresist formed on each wafer of the first lot isdeveloped. In step S305, each wafer of the first lot is etched using theresist pattern formed on the wafer as a mask. This forms a circuitpattern corresponding to the mask pattern in the shot-regions of eachwafer.

Afterwards, circuit patterns for upper layers are formed to complete adevice such as a semiconductor element. The above-describedsemiconductor device manufacturing method fabricates semiconductordevices having ultra-fine circuit patterns with a high throughput. Insteps S301 to S305, metal is deposited on the wafer through vapordeposition, resist is applied to the metal film, and then the processesin which the resist is exposed, developed, and etched are performed.Prior to these processes, a silicon oxide film may first be formed onthe wafer, the resist may be applied to the silicon oxide film, and theprocesses in which the resist is exposed, developed, and etched may thenbe performed.

Further, the exposure apparatus of the present embodiment may be used tofabricate a liquid crystal display device serving as a microdevice byforming a predetermined pattern (a circuit pattern or an electrodepattern) on a plate (glass substrate). One example of a method formanufacturing a liquid crystal display device will now be described withreference to a flowchart shown in FIG. 12. In FIG. 12, in a patternformation process S401, a mask pattern is transferred and exposed onto aphotosensitive substrate (e.g., a glass substrate coated with resist)with the exposure apparatus of the present embodiment. In other words, aphotolithography process is performed. Through the photolithographyprocess, a predetermined pattern including many electrodes is formed onthe photosensitive substrate. Afterwards, a predetermined pattern isformed on the substrate through processes including a developingprocess, an etching process, and a resist removing process. Then, acolor filter formation process is performed in step S402.

In the color filter formation process S402, a color filter is formed by,for example, arranging many sets of R (red), G (green), and B (blue)dots in a matrix, or arranging a plurality of sets of filters formed byR, G, and B stripes in horizontal scanning line directions. After thecolor filter formation process S402, a cell assembly process isperformed in step S403. In the cell assembly process S403, the substratehaving a predetermined pattern obtained through. the pattern formationprocess S401 and the color filter or the like obtained through the colorfilter formation process S402 are assembled together to form the liquidcrystal panel (liquid crystal cell).

In the cell assembly process S403, for example, liquid crystal isinjected between the substrate having the predetermined pattern obtainedthrough the pattern formation process S401 and the color filter obtainedthrough the color filter formation process S402 to form a liquid crystalpanel (liquid crystal cell). In a module assembly process performedsubsequently in step S404, an electric circuit for enabling theassembled liquid crystal panel (liquid crystal cell) to perform adisplay operation and other components including a backlight areattached to complete the liquid crystal display device With theabove-described liquid crystal display device manufacturing method, aliquid crystal display device having an ultra-fine circuit pattern ismanufactured with a high throughput.

The invention claimed is:
 1. A surface position detection apparatuswhich detects a position of a surface of a substrate placed on a stage,with respect to a direction intersecting the surface, on a basis of areceiving result of a light beam which is guided to the surface in adiagonal direction with respect to the surface and is reflected from thesurface, the apparatus comprising: a reflection member which reflectsthe light beam; and a depolarizer which is arranged in an optical pathof the light beam on a stage side relative to the reflection member andwhich depolarizes the light beam.
 2. The surface position detectionapparatus according to claim 1, wherein the depolarizer comprises awedge shaped prism formed from a birefringent crystal material.
 3. Thesurface position detection apparatus according to claim 1, wherein thedepolarizer comprises a deflection prism formed from a birefringentcrystal material.
 4. The surface position detection apparatus accordingto claim 2, wherein the birefringent crystal material comprisesmagnesium fluoride.
 5. The surface position detection apparatusaccording to claim 1, wherein the reflection member comprises a prismmember which reflects the light beam within the prism member.
 6. Thesurface position detection apparatus according to claim 5, wherein theprism member totally reflects the light beam.
 7. The surface positiondetection apparatus according to claim 1, wherein the reflection membercomprises a pair of reflection surfaces which reflects the light beamsequentially, the pair of reflection surfaces being arranged in parallelto each other.
 8. The surface position detection apparatus according toclaim 7, wherein the reflection member comprises a prism member havingthe pair of the reflection surfaces, and the pair of the reflectionsurfaces reflects the light beam within the prism member.
 9. The surfaceposition detection apparatus according to claim 7, wherein the pair ofthe reflection surfaces totally reflects the light beam.
 10. The surfaceposition detection apparatus according to claim 1, further comprising anoptical system arranged in the optical path of the light beam, theoptical system forming a position optically conjugate with the surfaceof the substrate, wherein the reflection member is arranged in theoptical path on a stage side relative to the optical system.
 11. Thesurface position detection apparatus according to claim 10, wherein theoptical system is a both-sides telecentric optical system.
 12. Thesurface position detection apparatus according to claim 1, furthercomprising: an optical member on which a predetermined pattern isformed; and a first optical system arranged in the optical path of thelight beam from the predetermined pattern so as to protect a first imageof the predetermined pattern onto the surface of the substrate in thediagonal direction, wherein the reflection member comprises a firstreflection member arranged within the first optical system, and whereinthe depolarizer comprises a first depolarizer arranged in the opticalpath on a stage side relative to the first reflection member.
 13. Thesurface position detection apparatus according to claim 12, wherein thefirst optical system is a both-sides telecentric optical system.
 14. Thesurface position detection apparatus according to claim 12, furthercomprising a second optical system arranged in the optical path of thelight beam from the first image so as to form a second image of thepredetermined pattern, wherein the reflection member further comprises asecond reflection member arranged within the second optical system, andwherein the depolarizer comprises a second depolarizer arranged in theoptical path on a stage side relative to the second reflection member.15. The surface position detection apparatus according to claim 14,wherein the second optical system is a both-sides telecentric opticalsystem.
 16. The surface position detection apparatus according to claim1, further comprising: an optical member on which a predeterminedpattern is formed; a first optical system arranged in the optical pathof the light beam from the predetermined pattern, so as to project afirst image of the predetermined pattern onto the surface of thesubstrate in the diagonal direction; and a second optical systemarranged in the optical path of the light beam from the first image soas to form a second image of the predetermined pattern, wherein thereflection member is arranged within the second optical system; andwherein the depolarizer is arranged in the optical path of the beam fromthe first image on a stage side relative to the reflection member. 17.The surface position detection apparatus according to claim 16, whereineach of the first and second optical systems is a both-sides telecentricoptical system.
 18. The surface position detection apparatus accordingto claim 14, further comprising a detection part which receives thelight beam from the second image and detects a lateral displacement ofthe second image on the basis of a receiving result of the light beamfrom the second image.
 19. The surface position detection apparatusaccording to claim 16, further comprising a detection part whichreceives the light beam from the second image and detects a lateraldisplacement of the second image on the basis of a receiving result ofthe light beam from the second image.
 20. A surface position detectionmethod of detecting a position of a surface of a substrate placed on astage, with respect to a direction intersecting the surface, on a basisof a receiving result of a light beam which is guided to the surface ina diagonal direction with respect to the surface and is reflected fromthe surface, the method comprising: reflecting the light beam by areflection member; and depolarizing the light beam by a depolarizerarranged in an optical path of the light beam on a stage side relativeto the reflection member.
 21. The surface position detection methodaccording to claim 20, wherein the reflection member comprises a prismmember which reflects the light beam within the prism member.
 22. Thesurface position detection method according to claim 21, wherein thelight beam is totally reflected by the prism member.
 23. The surfaceposition detection method according to claim 20, wherein the reflectionmember comprises a pair of reflection surfaces which reflects the lightbeam sequentially, the pair of reflection surfaces being arranged inparallel each to other.
 24. The surface position detection methodaccording to claim 23, wherein the reflection member comprises a prismmember having the pair of the reflection surfaces and the light beam isreflected by the pair of the reflection surfaces within the prismmember.
 25. The surface position detection method according to claim 23,wherein the light beam is totally reflected by the pair of thereflection surfaces.
 26. The surface position detection method accordingto claim 20, further comprising forming a position optically conjugatewith the surface of the substrate, wherein the light beam is reflectedby the reflection member arranged in the optical path on a stage siderelative to the optical system for forming the position opticallyconjugate with the surface of the substrate.
 27. The surface positiondetection method according to claim 20, further comprising: forming apredetermined pattern on an optical member; projecting a first image ofthe predetermined pattern onto the surface of the substrate in thediagonal direction by a first optical system arranged in the opticalpath of the light beam from the predetermined pattern; and wherein thelight beam from the predetermined pattern is reflected by the reflectionmember arranged within the first optical system.
 28. The surfaceposition detection method according to claim 27, further comprising:forming a second image of the predetermined pattern by a second opticalsystem arranged in the optical path of the light beam from the firstimage thereby forming the second image of the predetermined pattern,wherein the light beam reflected by the surface of the substrate isfurther reflected by the reflection member arranged within the secondoptical system.
 29. The surface position detection method according toclaim 20, further comprising: reflecting the light beam, and forming animage of the predetermined pattern by an optical system arranged in theoptical path of the light beam from the predetermined pattern, whereinthe optical system comprises a condensing optical system, wherein thelight beam reflected by the surface of the substrate is reflected by thereflection member arranged within the optical system.
 30. The surfaceposition detection method according to claim 28, further comprising:receiving the light beam from the second image; and detecting a lateraldisplacement of the second image on the basis of a receiving result ofthe light beam from the second image.
 31. The surface position detectionmethod according to claim 29, further comprising; and receiving thelight beam from the second image; and detecting a lateral displacementof the second image on the basis of a receiving result of the light beamfrom the second image.
 32. An exposure apparatus which exposes asubstrate with exposure light via a pattern, comprising: a substrateholding mechanism for holding the substrate; the surface positiondetection apparatus according to claim 1, the surface position detectionapparatus detecting a position of a surface to be exposed of thesubstrate held by the substrate holding mechanism; a driving unitdriving the substrate holding mechanism based on a detection resultobtained by the surface position detection apparatus to move thesubstrate held by the substrate holding mechanism; and an exposure ofthe substrate being performed under a condition in which the substrateis aligned by the driving unit.
 33. The exposure apparatus according toclaim 32, further comprising a projection optical system for forming theimage of the pattern, the surface position detection apparatus detectinga position of the surface to be exposed along an optical axis of theprojection optical system, the driving unit driving the substrateholding mechanism based on the detection result and at least one of amovement of the substrate in a direction along the optical axis and aleveling of the substrate being performed.
 34. The exposure apparatusaccording to claim 33, wherein the driving unit drives the substrateholding mechanism based on the detection result to move the substrate sothat the surface to be exposed is located within a focal depth of theprojection optical system.
 35. An exposure method for exposing asubstrate with exposure light via a pattern, comprising: detecting aposition of a surface to be exposed by utilizing the surface positiondetection apparatus according to claim 20; and moving the substratebased on a detection result of a position of the surface to be exposed,an exposure of the substrate being performed under a condition in whichthe substrate is aligned by the driving unit.
 36. The exposure methodaccording to claim 33, further comprising an projection forming theimage of the pattern on the surface to be exposed by the projectionoptical system, wherein a detection of a position of the surface to beexposed comprises a detection of a position of the surface to be exposedalong the optical axis of the projection optical system, and a movementof the substrate comprises the performance of at least one of themovement of the substrate along the direction of the optical axis andthe leveling of the substrate.
 37. The exposure method according toclaim 36, wherein the movement of the substrate comprises the movementof the substrate so as to locate the surface to be exposed within afocal depth of the projection optical system.
 38. A device manufacturingmethod of manufacturing a device having a circuit pattern, comprising:exposing a substrate with a pattern corresponding the circuit pattern byusing the exposure apparatus according to claim 32; and developing thesubstrate on which the pattern is exposed.
 39. A device manufacturingmethod of manufacturing a device having a circuit pattern, comprising;exposing a substrate with a pattern corresponding the circuit pattern byusing the exposure method according to claim 35; and developing thesubstrate on which the pattern is exposed.